libstdc++-v3/include/bits/postypes.h

   1 // Position types -*- C++ -*-
   2
   3 // Copyright (C) 1997, 1998, 1999, 2000, 2001, 2003, 2004
   4 // Free Software Foundation, Inc.
   5 //
   6 // This file is part of the GNU ISO C++ Library.  This library is free
   7 // software; you can redistribute it and/or modify it under the
   8 // terms of the GNU General Public License as published by the
   9 // Free Software Foundation; either version 2, or (at your option)
  10 // any later version.
  11
  12 // This library is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16
  17 // You should have received a copy of the GNU General Public License along
  18 // with this library; see the file COPYING.  If not, write to the Free
  19 // Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  20 // USA.
  21
  22 // As a special exception, you may use this file as part of a free software
  23 // library without restriction.  Specifically, if other files instantiate
  24 // templates or use macros or inline functions from this file, or you compile
  25 // this file and link it with other files to produce an executable, this
  26 // file does not by itself cause the resulting executable to be covered by
  27 // the GNU General Public License.  This exception does not however
  28 // invalidate any other reasons why the executable file might be covered by
  29 // the GNU General Public License.
  30
  31 //
  32 // ISO C++ 14882: 27.4.1 - Types
  33 // ISO C++ 14882: 27.4.3 - Template class fpos
  34 //
  35
  36 /** @file postypes.h
  37  *  This is an internal header file, included by other library headers.
  38  *  You should not attempt to use it directly.
  39  */
  40
  41 #ifndef _GLIBCXX_POSTYPES_H
  42 #define _GLIBCXX_POSTYPES_H 1
  43
  44 #pragma GCC system_header
  45
  46 #include <cwchar> // For mbstate_t
  47
  48 #ifdef _GLIBCXX_HAVE_STDINT_H
  49 #include <stdint.h> // For int64_t
  50 #endif
  51
  52 namespace std
  53 {
  54   // The types streamoff, streampos and wstreampos and the class
  55   // template fpos<> are described in clauses 21.1.2, 21.1.3, 27.1.2,
  56   // 27.2, 27.4.1, 27.4.3 and D.6. Despite all this verbage, the
  57   // behaviour of these types is mostly implementation defined or
  58   // unspecified. The behaviour in this implementation is as noted
  59   // below.
  60
  61 #ifdef _GLIBCXX_HAVE_INT64_T
  62   typedef int64_t       __streamoff_base_type;
  63 #else
  64   typedef long long     __streamoff_base_type;
  65 #endif
  66
  67   /// Integral type for I/O operation counts and buffer sizes.
  68   typedef ptrdiff_t     streamsize; // Signed integral type
  69
  70   template<typename _StateT>
  71     class fpos;
  72
  73   // Class streamoff is an implementation defined type that meets the
  74   // requirements for streamoff. It stores an offset as a signed
  75   // integer.  Note: this class is an implementation detail.
  76   class streamoff
  77   {
  78   private:
  79     __streamoff_base_type _M_off;
  80
  81   public:
  82     // Nothing in the standard requires that streamoff can be default
  83     // constructed. In this implementation a default constructor that
  84     // stores the value 0 is provided.
  85     streamoff()
  86     : _M_off(0) { }
  87
  88     // The standard only requires that streamoff can be constructed
  89     // from streamsize using the constructor syntax. This
  90     // implementation also allows implicit conversion from integer
  91     // types to streamoff.
  92     streamoff(__streamoff_base_type __off)
  93     : _M_off(__off) { }
  94
  95     // The standard requires that streamoff can be constructed from
  96     // instances of fpos using the constructor syntax, but gives no
  97     // semantics for this construction. In this implementation it
  98     // extracts the offset stored by the fpos object.
  99     // Note: In versions of GCC up to and including GCC 3.3, implicit
 100     // conversion from fpos to streamoff was allowed. This constructor
 101     // has now been made explicit to improve type safety.
 102     template<typename _StateT>
 103       explicit
 104       streamoff(const fpos<_StateT>&);
 105
 106     // The standard requires that streamsize can be constructed from
 107     // streamoff using the constructor syntax. This implementation
 108     // also allows implicit conversion. This allows streamoff objects
 109     // to be used in arithmetic expressions and to be compared against
 110     // each other and integer types.
 111     operator __streamoff_base_type() const
 112     { return _M_off; }
 113
 114     // This implementation allows the use of operators +=, -=, ++ and
 115     // -- on streamoff objects.
 116     streamoff&
 117     operator+=(__streamoff_base_type __off)
 118     {
 119       _M_off += __off;
 120       return *this;
 121     }
 122
 123     streamoff&
 124     operator-=(__streamoff_base_type __off)
 125     {
 126       _M_off -= __off;
 127       return *this;
 128     }
 129   };
 130
 131   /**
 132    *  @brief  Type used by fpos, char_traits<char>, and char_traits<wchar_t>.
 133    *
 134    *  @if maint
 135    *  In clauses 21.1.3.1 and 27.4.1 streamoff is described as an
 136    *  implementation defined type. In this implementation it is a
 137    *  distinct class type.
 138    *  Note: In versions of GCC up to and including GCC 3.3, streamoff
 139    *  was typedef long.
 140    *  @endif
 141   */
 142   typedef class streamoff streamoff;
 143
 144   /**
 145    *  @brief  Class representing stream positions.
 146    *
 147    *  The standard places no requirements upon the template parameter StateT.
 148    *  In this implementation StateT must be DefaultConstructible,
 149    *  CopyConstructible and Assignable.  The standard only requires that fpos
 150    *  should contain a member of type StateT. In this implementation it also
 151    *  contains an offset stored as a signed integer.
 152    *
 153    *  @param  StateT  Type passed to and returned from state().
 154    */
 155   template<typename _StateT>
 156     class fpos
 157     {
 158     private:
 159       friend class streamoff;
 160
 161       __streamoff_base_type     _M_off;
 162       _StateT                   _M_state;
 163
 164     public:
 165       // The standard doesn't require that fpos objects can be default
 166       // constructed. This implementation provides a default
 167       // constructor that initializes the offset to 0 and default
 168       // constructs the state.
 169       fpos()
 170       : _M_off(0), _M_state() { }
 171
 172       // The standard requires implicit conversion from integers to
 173       // fpos, but gives no meaningful semantics for this
 174       // conversion. In this implementation this constructor stores
 175       // the integer as the offset and default constructs the state.
 176       /// Construct position from integer.
 177       fpos(__streamoff_base_type __off)
 178       : _M_off(__off), _M_state() { }
 179
 180       // The standard requires that fpos objects can be constructed
 181       // from streamoff objects using the constructor syntax, and
 182       // fails to give any meaningful semantics. In this
 183       // implementation implicit conversion is also allowed, and this
 184       // constructor stores the streamoff as the offset and default
 185       // constructs the state.
 186       /// Construct position from offset.
 187       fpos(const streamoff& __off)
 188       : _M_off(__off), _M_state() { }
 189
 190       /// Remember the value of @a st.
 191       void
 192       state(_StateT __st)
 193       { _M_state = __st; }
 194
 195       /// Return the last set value of @a st.
 196       _StateT
 197       state() const
 198       { return _M_state; }
 199
 200       // The standard only requires that operator== must be an
 201       // equivalence relation. In this implementation two fpos<StateT>
 202       // objects belong to the same equivalence class if the contained
 203       // offsets compare equal.
 204       /// Test if equivalent to another position.
 205       bool
 206       operator==(const fpos& __other) const
 207       { return _M_off == __other._M_off; }
 208
 209       /// Test if not equivalent to another position.
 210       bool
 211       operator!=(const fpos& __other) const
 212       { return _M_off != __other._M_off; }
 213
 214       // The standard requires that this operator must be defined, but
 215       // gives no semantics. In this implemenation it just adds it's
 216       // argument to the stored offset and returns *this.
 217       /// Add offset to this position.
 218       fpos&
 219       operator+=(const streamoff& __off)
 220       {
 221         _M_off += __off;
 222         return *this;
 223       }
 224
 225       // The standard requires that this operator must be defined, but
 226       // gives no semantics. In this implemenation it just subtracts
 227       // it's argument from the stored offset and returns *this.
 228       /// Subtract offset from this position.
 229       fpos&
 230       operator-=(const streamoff& __off)
 231       {
 232         _M_off -= __off;
 233         return *this;
 234       }
 235
 236       // The standard requires that this operator must be defined, but
 237       // defines it's semantics only in terms of operator-. In this
 238       // implementation it constructs a copy of *this, adds the
 239       // argument to that copy using operator+= and then returns the
 240       // copy.
 241       /// Add position and offset.
 242       fpos
 243       operator+(const streamoff& __off) const
 244       {
 245         fpos __pos(*this);
 246         __pos += __off;
 247         return __pos;
 248       }
 249
 250       // The standard requires that this operator must be defined, but
 251       // defines it's semantics only in terms of operator+. In this
 252       // implementation it constructs a copy of *this, subtracts the
 253       // argument from that copy using operator-= and then returns the
 254       // copy.
 255       /// Subtract offset from position.
 256       fpos
 257       operator-(const streamoff& __off) const
 258       {
 259         fpos __pos(*this);
 260         __pos -= __off;
 261         return __pos;
 262       }
 263
 264       // The standard requires that this operator must be defined, but
 265       // defines it's semantics only in terms of operator+. In this
 266       // implementation it returns the difference between the offset
 267       // stored in *this and in the argument.
 268       /// Subtract position to return offset.
 269       streamoff
 270       operator-(const fpos& __other) const
 271       { return _M_off - __other._M_off; }
 272     };
 273
 274   /// Construct offset from position.
 275   template<typename _StateT>
 276     inline
 277     streamoff::streamoff(const fpos<_StateT>& __pos)
 278     : _M_off(__pos._M_off) { }
 279
 280   // Clauses 21.1.3.1 and 21.1.3.2 describe streampos and wstreampos
 281   // as implementation defined types, but clause 27.2 requires that
 282   // they must both be typedefs for fpos<mbstate_t>
 283   /// File position for char streams.
 284   typedef fpos<mbstate_t> streampos;
 285   /// File position for wchar_t streams.
 286   typedef fpos<mbstate_t> wstreampos;
 287 } // namespace std
 288
 289 #endif